Swash-type impeller pumps

ABSTRACT

In a swash-type impeller shredder pump, a method and means for varying the spacing of the stationary cutter bars cooperative with the serrated swash-type impeller in a combined pumping and shredding operation.

United States Patent 1191 Rosenquest, Jr.

SWASH-TYPE IMPELLER PUMPS Inventor: John B. Rosenquest, Jr., New

Canaan,Conn.

Assignee: Dorr-Oliver Incorporated, Stamford,

Conn.

Filed: May 8, 1972 Appl. No.: 250,929

Int. Cl. B0 2c 13/10 Field of Search 241/15, 46.11, 73, 241/84, 86, 88, 89.1, 89.2, 89.3, 185 A, 245, 261

14 1 Jan. 15, 1974 References Cited UNITED STATES PATENTS 953,111 3/1910 Williams ..241/88 3,722,804 3/1973 Petersen ..241 73 Primary ExaminerGranville Y. Custer, .lr. Attorney-Burtsell J. Kearns and Theodore M. Jablon 57 ABSTRACT In a swash-type impeller shredder pump, a method and means for varying the spacing of the stationary cutter bars cooperative with the serrated swash-type impeller in a combined pumping and shredding operatlon.

16 Claims, 20 Drawing Figures FIG.

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I l L COVER LINER BARS FIG.

1 SWASHJIY PE IMPELLER PUMPS This invention relate to improvements in rotary pumps having a swash-type impeller, as such capable of As exemplified in the Neidl us. Pat. Nos. 2,956,503;

3,005,597; 3,060,862; 3,067,960; and 3,329,354, the swash plate is fixed upon the inner end of an impeller shaft, inclined relative to the impeller axis. This swash plate is surrounded closely by a cylindrical pump housing, coaxial with the shaft, and when rotated at suitable speed provides centrifugal pumping action by drawing liquid through an axially disposed inlet neck of the pump housing, and discharging through a lateral outlet neck from the cylindrical body portion of the housing.

More particularly, this invention is concerned with the type of Neidl pump wherein the pumping action of the swash plate impeller is combined with a shredding, cutting-, or shearingaction upon lumps or clusters of solid material carried by the liquid being pumped. For that purpose, the side edges of the swash plate are formed with serrations or teeth cooperating with complementary cutting grooves provided internally of the cylindrical body portion of the pump housing. Accordingly, the stationary cutting grooves extend in parallel planes perpendicular to the pump axis, and shredding is due to the shearing or tearing action of the teeth entering respective grooves. In the shredder type of pump embodying this invention, the cutting grooves are provided upon cutter bars somewhat resembling toothed racks. These cutter bars extend parallel to one another, spaced about the pump axis, constituting a cylindrical cage construction herein termed the cutter cage, fitted into the surrounding cylindrical body portion of the pump housing. I

This invention may be embodied in the Neidl type of shredder pump wherein the cylindrical cutter cage is split longitudinally. Each of the semicylindrical component structures of the cutter cage comprises a semicircular segment or rim member at each end, fixed to the inner faces of the cutter bars by means of suitably arranged bolt connections.

Accordingly, the cross-sectional profile of the cutter bars is curved so as to conform to the outer cylindrical curvature of the rim members to which they are fixed by means of screw bolts threaded into the rims, and with their heads counter-sunk into the respective outer faces of the bars.

To accommodate the bipartite cutter cage, the cylindrical housing portion is similarly split, so that a semicircular cover portion thereof is removable or swingable away from a fixed discharge housing portion about an axis parallel to the axis of the impeller shaft. This allows for access and inspection of the interior of the pump without requiring disconnection of the inletand the discharge ends of the pump housing.

Thus, when the cover section of the pump housing is swung to the open position, it contains secured therein the one half or component structure of the cutter cage. The complementary half of the cutter cage is secured in the fixed discharge section of the pump housing.

In the fixed discharge housing section the cutter bars must be constructed and arranged so as to provide discharge passages for the solids-bearing liquid being pumped. As contemplated bythis invention, the passages are provided by way of appropriate dimensioning and spacing of the cutter bars from one another, which spacing depends upon the extent to which the solids are to be reduced by the shredding action, as well as upon other operational conditions, such as the nature of the solids and the nature or viscosity of the carrier liquid.

in view of the foregoing pump operating conditions, this invention is concerned with the problem of providing a cutter cage construction wherein the spacing between the identically dimensioned cutter bars and thus the width of the throughfiow discharge passages, should be variable over a wide range, providing for a maximum of options of intermediate graduated bar spacing increments.

One way to meet this problem has been to provide a basic assembly of cutter bars of standardized dimensions, with a bolt hole on center at each end, and with a bar spacing considered adequate to provide the discharge flow passagesadequate to meet the conditions of an intended pumping-shredding operation. If in the actual pumping operation, because of plugging of the discharge passages or slats, a wider spacing of the cutter bars was indicated, then it would be possible to have the width of the bars themselves reduced by an expensive and time-consuming grinding operation. The working hardness of the material added to the basically high cost of the precision molds for the investment casting process whereby these cutter bars are produced, makes this an impractical and limited solution of the bar spacing problem.

Another approach to the problem is to interpose additional threaded bolt holes between those provided upon the rim members for a basic cutter bar assembly, and to devise a system whereby different combinations of bolt holes might be selected, to allow the cutter bars to be assembled in different space relationships. This approach, too, has its practical limitations, since only a limited number of the threaded bolt holes can be accommodated. Furthermore, only a very limited number of cutter bar combinations would then be available, providing a number of increments, inadequate to meet specific operating requirements or graduations.

Still another approach has been to provide an expensive inventory of cutter bars of different widths to meet different graduation bar spacing requirements, considering also the high cost of the molds required for investment casting of these parts.

The object of this invention, therefore, is to provide an improved cutter cage construction composed of cutter bars of uniform standardized dimensions, yet capable of being arranged and rearranged in such a manner as to meet, without incurring the aforementioned limitations, costs and complications, a much greater number of bar spacing requirements over a wide range of widths, than has heretofore been attainable, thereby rendering the pump operation more efficient, and the pump more closely adaptable to a greater variety of operating conditions.

To attain the foregoing objective, the segment rim members of the cage portion associated with the discharge section of the pump, are provided with a row of threaded bolt holes, spaced as closely as is practical.

This allows for a series of cutter bars of a practical width, and of suitably standardized dimensions to be assembled in a basic closely spaced relationship, with threaded bolt holes available between those occupied by the cutter bars, all holes being equally spaced from one another.

With this narrowly spaced cutter bar assembly as a basis, the invention aims to make available a larger number of relatively smaller bar spacing increments within a given overall range, as compared with those at best heretofore considered or available.

To this end the invention provides cutter bars of uniform overall dimensions wherein the bolt holes are offset from the longitudinal center line of the bar. In the preferred embodiment, that distance is equal to one quarter of the center-to-center distance between any two mutually adjoining threaded holes.

With these off-center cutter bars reversible end-forend, and various selected combinations of threaded bolt holes in the rim members thus available, a novel system of bar spacing options presents itself, whereby bar spacing requirements may be met, sufficiently differentiated for all intended practical conditions.

A maximum of differentiated spacings or options can be achieved by way of various combinations of offcenter cutter bars with those having the bolt holes on the center line, thus overcoming limitations imposed by the spacing of the available threaded holes themselves, while avoiding the aforementioned earlier disadvantages and costs.

Other features and advantages will hereinafter appear.

FIG. I is a longitudinal part-sectional view of the pump, showing the serrated swash-type impeller plate cooperating with the cutter bars of the surrounding cutter cage.

FIG. la is a detail plan view of the serrated swash plate of the impeller.

FIG. lb is a side view of the .swash plate taken on line lb lb in FIG. la.

FIG. 2 is an end view upon the inlet end of the pump, taken on line 2-2 in FIG. 1, with parts-broken away, showing the split construction of the pump housing and of the cutter cage.

FIG. 2a is a fragmentary detail view, taken on line 2a-2a in FIG. 2.

FIG. 3 is an enlarged longitudinal sectional detail view of the cylindrical cutter cage taken from FIG. 1.

FIG. 3a is an enlarged detail view of the composite bipartite rim of the cutter cage, taken from FIG. 3.

FIG. 3b is a plan view of the rim, taken on line 3b 3b in FIG. 3a.

FIG. 4 is a cross-sectional view of the cutter cage, taken on line 4-4 in FIG. 3, showing one example of cutter bar spacing selected from available options.

FIG. 5 is a crosssectional view of the cutter cage, taken on line 5-5 in FIG. 3.

FIG. 6 is an end view of the cutter cage, taken on line 66 in FIG. 3.

FIG. 7 is a plan view of a cutter bar with bolt holes arranged on the center.

FIG. 7a is a cross-sectional view taken on line 7a 7a in FIG. 7.

FIG. 8 is a plan view of a cutter bar with bolt holes offset to the left of center.

FIG. 8a is a cross-sectional view taken on line 8a 8a in FIG. 8.

FIG. 9 is a plan view of a cutter bar with bolt holes offset to the right of center.

FIG. 9a is a cross-sectional view taken on line 9a 9a in FIG. 9.

FIGS. 10 and 11 are diagrammatic illustrations of a preferred embodiment of the invention, showing the number of available bar spacing options for the cutter cage.

FIG. 12 shows the bar spacing options of FIGS. 10 and 11, in tabulated form.

As exemplified in the accompanying drawings, the invention is embodied in a swash-type impeller shredder pump of generally known construction.

In such a pump, the pump housing comprises an intermediate cylindrical body portion 10 longitudinally divided in a plane 11 (see FIG. 2). Thus divided the body portion comprises a discharge section 12 formed with a footing l3, and with an upwardly directed pump discharge neck 14, and a complementary cover section 15. A hinge connection 16 allows the cover section to be swung away from the discharge section, after loosening bolts 17 and 18, the open position of the cover being shown in dotted lines.

A rearward end plate 19 formed with a pump inlet neck 20 has a flangeand bolt connection 21 with the body portion of the housing.

a forward end plate 22 has a flange connection 23 with the forward end of the body portion of the housing. The bolts 23a of this flange connection also hold the flange of a bearing structure 24 carrying an impeller shaft 25, and formed with a base portion 26 complementary to footing 13.

The impeller shaft extends into the pump housing by way of a combined bearing and stuffing box 27 provided on the forward end plate 22. Upon the inner end of the shaft is mounted a swash-type impeller which may be in the form of the well-known swash impeller plate 28 inclined at an angle of about 45.

The lateral edges of the impeller plate 28 are formed with serrations or teeth 28a (see FIGS. la and 1b) in such a manner as to cooperate with corresponding cutting grooves 28b provided internally by a cylindrical cutter cage 29 formfitted into the cylindrical body portion of the pump housing.

Rotation of the impeller shaft produces a combined centrifugal pumpingand shredding action upon solids or lumps of material carried by the liquid handled by the pump. Particles of the material sufficiently reduced by the shredding or shearing action, will pass, together with the carrier liquid, through longitudinal elongate discharge flow passages provided in the cutter cage and extending parallel to the pump axis.

The cutter cage is longitudinally divided in a plane that coincides with the split of the surrounding cylindrical body portion of the housing. Both semi-cylindrical halves or sectors 30 and 31 of this bipartite cutter cage are secured in the respective sections of the housing by means of a pair of holding screws 32 at one side, and a pair of holding screws 33, opposite thereto (see FIGS. 2, 2a, 4 and 6). The cage sectors are therefore herein termed the cover sector 30 and the discharge sector 31 respectively, the latter providing the elongate discharge flow passages communicating with the discharge neck of the pump housing.

The cover sector 30 of the cutter cage comprises a pair of half-round rim members or l-segments 30a and 30b (see FIG. 3) rigidly interconnected by cutter bars 36 having inwardly projecting transverse cutter teeth 37. The cutter bars extending parallel to the pump axis, have arcuate cross-sectional configuration (see also FIGS. 4, 5, 6 and FIGS. 7a, 8a, 9b) conforming to the outer cylindrical curvature of the rim members, as well as to the inner curvature of housing cover 15 wherein this cage sector is being held. Each cutter bar has a bolt hole at each end, accommodating a fastening screw 38 for rigidly connecting the cutter bars to the outer face of the rim members, with conical screw heads counter-sunk in the outer arcuate surface of the bars.

The cover sector 30 of the cage thus represents a hollow semi-cylindrical structure, with only a narrow tolerance space 39 (see FIG. 4) separating the cutter bars from one another, but closed by the associated cover section of the housing. An. arrangement such as exem: plified in FIG. 4 comprises an uneven number of the cutter bars 36, with the two longer holding screw bolts 32 (see FIGS. 2, 3b, 4, and 5) taking the place of the shorter fastening screws 38 in the respective rim members 30a and 30b (see FIG. 3).

The complementary cage sector or discharge sector 31 has rim segments 31a and 31b, with cutter bars having identical overall dimensions equal to those of cover sector 30 of the cage. However, in this discharge sector 31, provision is made to allow the cutter bars to be spaced by graduated increments, in order thereby to provide between the bars elongate discharge flow passages of corresponding optionally selected widths. With spacing 8-1 as exemplified in FIGS. 4, 5 and 6, there are only six cutter bars occupying the space that would otherwise accommodate seven such bars in the aforementioned basic closely spaced relationship.

The cutter bar spacing 8-1 in the example of FIG. 4 is selected as the first of six available options or Arrangements l to 6 compiled in the tabulation of FIG. 12, and visually represented in the schematic version of FIGS. 10 and 11. With threaded bolt holes I to 19 available in the rim segments of cage sector 31 (see also FIG. 3a and FIG. 3b) these options are based upon the feature that some of the cutter bars have the bolt holes located on center, while others have the bolt holes located off-center a distance d equal to one quarter of the center to-center distance between any two mutually adjacent threaded holes (see FIG. 4, as well as FIGS. 7, 8, 9 and 7a, 8a, 9a).

Accordingly, with respect to location of the bolt holes (accommodating the fastening screws 38), the cutter bars are identified in the schedule of FIG. 12, as: R Cutter bar with bolt holes offset to the right (see FIGS. 9 and 9a) L Cutter bar with bolt holes offset to the left (see FIGS. 8 and 8a) C Cutter bar with bolt holes located on center (see FIGS. 7 and 7a) Reverting to the cutter bar combination of the FIG. 4 example, this is the Arrangement No. I appearing as such in the Tabulation of FIG. 12, as well as the schematic version of FIG. 10. This represents a bar spacing 5-1 of three-eighths inch indicated for a practical cage diameter D=l-% inches. As seen from FIG. 4 and FIG. 10, this combination has six cutter bars assigned to respective threaded holes Nos. 2, 5, 8, 12, I and 18, with the spacing in the middle adequate to accommodate therein the holding screw bolts 33 (see also FIGS. 2, 4, and 6).

Accordingly, the first cutter bar in this combination assigned to threaded holes No. 2 is identified (FIG. 4

and FIG. 10) as R-2 thereby designating its position on the rim member. The remaining five cutter bars are similarly designated as C-S, L-8, R-12, C-l5, and L-18.

Similar designations are applied to' the remaining available cutter bar combinations as shown in the schematic version of FIG. 10, to designate their positions. These combinations or Arrangements No. 2 to 6 (see 5 FIG. 12) provide graduated bar spacings of 9/ l6, "A, 1-54, I-7/l6, and 2-% inches respectively, generally designated as spaces 8-2, 8-3, 5-4, 8-5, and 8-6 respectively in FIG. llfl.

From the foregoing example or a preferred embodiment it will be seen that the invention provides a desired number of practical bar spacing options, to meet a variety of pump operating requirements, whereby the respective cutter bar combinations can be assembled and established readily and inexpensively, without incurring the aforementioned drawbacks, costs, and complications.

To meet such diverse or differentiated operating requirements in a preferred embodiment, practical aids to establish a desired cutter bar combination are provided in the form of the tabulation of FIG. 12, and the schematic version of FIGS. 10 and I 1, whereby desired combinations of R-bars, L-bars, and C-bars can be readily established. In this embodiment, the threaded holes in the rim segments of the discharge cage sector 31 are closely spaced, the spacing being in relation to the width of the cutter bars so that these bars may be accommodated in the available arcuate space of cage sector 31 in a basic mutually adjoining relationship.

The graduations or permutations of the bar spacings made available by this invention, will enable an operator to make field adjustments to establish the most efficient setting of the cutter bars, in order to obtain optimum results for given operating conditions.

According to one example, in the manufactureof rubber-based adhesives, the shredder-type pump embodying this invention may be employed in circuit with the mixing vessel. In this batch-type process, the rubberbased adhesives are manufactured by adding various types of rubber such as natural, synthetic, or milled rubber to solvents and resins in the mixing vessel, and mixing until all of the rubber gel has been dispersed in the solvent, with the shredder pump operating in closed circuit with the mixing vessel. While the pump will accept any piece of rubber that will pass through the pipe leading to its suction inlet neck, the cutter bar spacing may be such as to present too much of an obstruction to the passage of the rubber.

Thus, while the solvent can pass on through the spacing easily, the rubber is detained while being exposed to the shredding action until reduced to small pieces. Consequently, in rubber solutions where the rubber content may be in the order of 25 percent by weight or more, the interior of the cutter cage may become filled with rubber causing the flow to stop and necessitating selecting a cutter spacing large enough to pass the rubber after partial disintegration has been accomplished. In this way a suitable operating equilibrium is attainable whereby the operation of the pump is rendered self-clearing.

However, in the selection of the cutter bar spacing a further consideration relates to the total efficiency of the rubber dispersion process, in view of the fact that the dispersion process is not complete until the last of the rubber has been dispersed in the operation of the circuit, and furthermore, that the dispersion time is a function of the size of the largest piece of rubber to be dispersed. Therefore, in the practice of this invention,

an optimum bar spacing can be selected, which is neither too narrow nor too wide, for attaining nonclogging operation at minimum dispersion time.

I claim:

1. In the operation of a rotary pump with a housing having a cylindrical body portion longitudinally divided into a fixed section provided with a discharge neck, and a removable arcuate cover section, a forward end closure member having an inlet neck, detachably connected to the forward end face of said cylindrical body portion, and an opposite end closure member detachably connected to the rearward endface of said body portion,

an impeller shaft extending through said rearward closure member, and having an inner end terminating within said housing, and a serrated swash-type impeller mounted on said inner end of the impeller shaft, cooperating with toothed cutter bars in a combined pumpingand shredding operation incident to rotation of the impeller shaft,

said cutter bars being assembled in the form of an open ended cutter cage formfitted into said cylindrical body portion, and longitudinally divided so that one arcuate cage section is contained in said housing cover section, and the complementary arcuate cage section is contained in said fixed housing section, with the cutter bars spaced so as to provide between them elongate discharge fiow passages communicating with said discharge neck, the ends of said cutter bars being fixedly connected to the cylindrical outer faces of respective semiperipheral rim members by means of screw bolts threaded into said rim members,

the method of varying the spacing of said cutter bars,

and thereby varying the width of said flow passages, which comprises providing additional threaded holes between those occupied by said bolts, to constitute a row of evenly and closely spaced threaded holes,

providing offset cutter bars with their bolt holes offset a distance from the center line, said distance being equal to one fourth of the distance between any two mutually adjoining threaded holes of said row, said cutter bars being reversible end for end, for placing the offset either to the right or to the left,

and combining a required number of offset cutter bars into cage assemblies in accordance with selected combinations of said threaded holes, so as to establish any one of the thus available bar spacing options in said complementary section of the cutter cage.

2. The method according to claim 1, which comprises additionally providing non-offset cutter bars having their bolt holes located on the center line, and combining offset cutter bars together with one or more of the non-offset cutter bars in accordance with selected combinations of said threaded holes, so as to provide corresponding additionally available bar spacing options.

3. The method according to claim 1, wherein said row comprises a basic series of threaded holes basically spaced so as to accommodate said cutter bars in narrowly spaced relationship, and wherein said additional holes are interposed between any two of said basically spaced holes, whereby a corresponding series of options of graduated bar spacing increments is attainable beyond said narrowly spaced relationship of the cutter bars.

4. In the operation of a rotary pump with a housing having a cylindrical body portion longitudinally divided into a fixed section provided with a discharge neck, and a removable arcuate cover section, a forward end closure member having an inlet neck, detachably connected to the forward end face of said cylindrical body portion, and an opposite end closure member detachably connected to the rearward end face of said body portion,

an impeller shaft extending through said rearward closure member, and having an inner end terminating within said housing, and a serrated swash-type impeller mounted on said inner end of the impeller shaft, cooperating with toothed cutter bars in a combined pumpingand shredding operation incident to rotation of the impeller shaft,

said cutter bars being assembled in the form of an open ended cutter cage formfitted into said cylindrical body portion, and longitudinally divided so that one arcuate cage section is contained in said housing cover section, and the complementary arcuate cage section is contained in said fixed housing section, with the cutter bars spaced so as to provide between them elongate discharge flow passages communicating with said discharge neck, the ends of said cutter bars being fixedly connected to the cylindrical outer faces of respective semiperipheral rim members by means of screw bolts threaded into said rim members,

the method of varying the spacing of said cutter bars,

and thereby varying the width of said fiow passages, which comprises,

providing additional threaded holes between those occupied by said bolts, to constitute a row of evenly and closely spaced threaded holes, comprising one centrally arranged hole and an equal number of holes symmetrically disposed on either side of th central hole, the

providing offset cutter bars with their bolt holes offset a distance from the center line, said distance being equal to one-fourth of the distance between any two mutually adjoining threaded holes of said row, said cutter bars being reversible end for end, for placing the offset either to the right or to the left,

and combining a required number of offset cutter bars into cage assemblies in accordance with selected combinations of said threaded holes, so as to establish any one of the thus available bar spacing options in said complementary section of the cutter cage.

5. The method according to claim 4, which comprises additionally providing non-offset cutter bars having their bolt holes located on the center line, and combining offset cutter bars together with one or more of the non-offset cutter bars in accordance with selected combinations of said threaded holes, so as to provide corresponding additionally available bar spacing options.

6. The method according to claim 4, which comprises providing said row having a basic series of threaded holes basically spaced for accommodating a series of cutter bars in narrowly spaced relationship and occupying said rim members substantially from end to end, and wherein said additional holes are interposed between any two of said basically spaced holes, whereby a corresponding series of options of graduated bar spacing increments is attainable beyond said narrowly spaced relationship of the cutter bars.

7. The method according to claim 4, which comprises providing said row to have a basic series of threaded holes basically spaced so as to accommodate said cutter bars in narrowly spaced relationship, and wherein a pair of additional threaded holes are interposed and accommodated between any two of said basically spaced holes, and occupying said rim members substantially from end to end, whereby a corresponding series of options of graduated bar'spacing increments is attainable beyond said narrowly spaced relationship of the cutter bars.

8. The method according to claim 4, which comprises providing said row to have holes numbered 1 through 19 including seven basic holes numbered 1, 4, 7, 10,

' 13, 16 and 19 basically spaced for accommodating a series of cutter bars in narrowly spaced relationship, and substantially occupying said rim members from end to end, whereby options of graduated bar spacing increments are attainable, with R designating an offset cutter bar having bolt holes offset to the right of center line, L designating an offcenter cutter bar having bolt holes offset to the left of center line, and C designating a non-offset cutter bar having bolt holes located on center, said options comprising 1. Cutter bars R, C, L, R, C, L connected to threaded holes 2, 5, 8, 12, and 18 respectively. 2. Cutter bars L, R, L, R, L, R connected to threaded holes 1, 5, 8, 12, 15 and 19 respectively. 3. Cutter bars L, L, L, L, L connected to threaded holes 2, 6, 10, 14 and 18 respectively. 4. Cutter bars L, R, C, L, R connected to threaded holes 1, 6, 10, 14 and 19 respectively. 5. Cutter bars L, R, L, R,'L connected to threaded holes 1, 6, 10, 15 and 19 respectively. I 6. Cutter bars L, L, L, L connected to threaded holes 1, 7, 13 and 19 respectively. 9. A rotary pump with a housing having a cylindrical body portion longitudinally divided into a fixed section provided with a discharge neck, and a removable arcuate cover section, a forward end closure member having an inlet neck, detachably connected to the forward end face of said cylindrical body portion, and an opposite end closure member detachably connected to the rearward end face of said body portion,

an impeller shaft extending through said rearward closure member, and having an inner end terminating within said housing, and a serrated swash-type impeller mounted on said inner end of the impeller shaft, cooperating with a toothed cutter bars in a combined pumpingand shredding operation incident to rotation of the impeller shaft.

said cutter bars being assembled in the form of an open ended cutter cage formfitted into said cylindrical body portion, and longitudinally divided so that one arcuate cage section is contained in said housing cover section, and the complementary arcuate cage section is contained in said fixed housing section, with the cutter bars spaced so as to provide between them elongate discharge flow passages communicating with said discharge neck, the ends of said cutter bars being fixedly connected to the cylindrical outer faces of respective semiperipheral rim members by means of screw bolts threaded into said rim members,

characterized in that the discharge section of the cage comprises a pair of semi-peripheral end rim members each provided with a row of closely spaced radially directed threaded holes, comprising one centrally arranged hole and equal numbers of identical threaded holes, disposed symmetrically on either side of the central hole, an arrangement of off-center cutter bars connected to said rim members through offcenter bolt holes in said cutter bars, located off center a distance equal to one quarter of the distance between any two mutually adjacent threaded holes, with the offsets disposed in accordance with a predetermined flow passage spacing between said bars.

10. A rotary pump with a housing having a cylindrical body portion longitudinally divided into a fixed section provided with a discharge neck, and a removable arcuate cover section, a forward end closure member having an inlet neck, detachably connected to the forward end face of said cylindrical body portion, and an opposite end closure member detachably connected to the rearward end face of said body portion,

an impeller shaft extending through said rearward closure member, and having an inner end terminating within said housing, and a serrated swash-type impeller mounted on said inner end of the impeller shaft, cooperating with toothed cutter bars in a combined pumpingand shredding operation incident to rotation of the impeller shaft,

said cutter bars being assembled in the form of an openended cutter cage formfitted into said cylindrical body portion, andlongitudinally divided so that one arcuate cage section is contained in said housing cover section, and the complementary arcuate cage section is contained in said fixed housing section, with the cutter bars spaced so as to provide between them elongate discharge flow passages communicating with said discharge neck, the ends of said cutter bars being fixedly connected to the cylindrical outer faces of respective semiperipheral rim members by means of screw bolts threaded into said rim members,

characterized in that the discharge section of the cage comprises a pair of semi-peripheral end rim members each provided with a row of closely spaced radially directed threaded holes, comprising one centrally arranged hole and equal numbers of identical threaded holes, disposed symmetrically on either side of the central hole, and an arrangement of cutter bars, which in turn comprises offcenter cutter bars connected to said rim members, said cutter bars located off center a distance equal to one quarter of the distance between any two mutually adjacent threaded holes, and at least one non-offcenter cutter bar, all of said cutter bars being combined and with said offsets disposed in accordance with a predetermined flow passage spacing between said bars.

11. The pump according to claim 10 wherein said row comprises at least 19 threaded holes numbered 1 through 19, including seven basically spaced holes assigned to numbers 1, 4, 7, 10, 13, 16 and 19 of said row, and an assembly of cutter bars with R designating a cutter bar having bolt holes offset to the right, L designating bolt holes offset to the left, and C designating a cutter bar with bolt holes on center, said assembly comprising Cutter bars R, C, L, R, C, L connected to threaded holes 2, 5, 8, l2, l and 19 respectively.

12. The pump according to claim wherein said row comprises at least 19 threaded holes numbered 1 through 19, including seven basically spaced holes assigned to numbers 1, 4, 7, 10, 13, 16, and 19 of said row, and an assembly of cutter bars with R designating a cutter bar having bolt holesoffset to the right, L designating bolt holes offset to the left, and C designating a cutter bar with bolt holes on center, said assembly comprising cutter bars L, R, L, R, L, R connected to threaded holes 1, 4, 8, 12, and 19 respectively.

13. The pump according to claim 10 wherein said row comprises at least 19 threaded holes numbered 1 through 19, including seven basically spaced holes assigned to numbers 1, 4, 7, 10, l3, l6, and 19 of said row, and an assembly of cutter bars with R designating a cutter bar having bolt holes offset to the right, L designating bolt holes offset to the left, and C designating a cutter bar with bolt holes on center, said assembly comprising cutter bars L, L, L, L, L connected to threaded holes 2, 6, 10, 14 and 18 respectively.

14. The pump according to claim 10, wherein said row comprises at least 19 threaded holes numbered 1 through 19, including seven basically spaced holes assigned to numbers 1, 4, 7, 10, 13, 16 and 19 of said row, and an assembly of cutter bars with R designating a cutter bar having bolt holes offset to the right, L designating bolt holes offset to the left, and C designating a cutter bar with bolt holes on center, said assembly comprising cutter bars L, R, C, L, R connected to threaded holes 1, 6, l0, l4 and 19 respectively.

15. The pump according to claim 10, wherein said row comprises at least 19 threaded holes number 1 through 19, including seven basically spaced holes assigned to number 1, 4, 7, l0, 13, 16 and 19 of said row, and an assembly of cutter bars with R designating a cutter bar having bolt holes offset to the right, L designating bolt holes offset to the left, and C designating a cutter bar with bolt holes on center, said assembly comprising cutter bars L, R, L, R, L connected to threaded holes 1, 6, l0, l5 and 19 respectively.

16. The pump according to claim 10, wherein said row comprises at least 19 threaded holes number 1 through 19, including seven basically spaced holes assigned to numbers 1, 4, 7, 10, 13, 16 and 19 of the said row, and an assembly of cutter bars with R designating a cutter bar having bolt holes offset to the right, L designating bolt holes offset to the left, and C designating a cutter bar with bolt holes on center, said assembly comprising cutter bars L, L, L, L connected to threaded holes 1,

7, l3 and 19 respectively. 

1. In the operation of a rotary pump with a housing having a cylindrical body portion longitudinally divided into a fixed section provided with a discharge neck, and a removable arcuate cover section, a forward end closure member having an inlet neck, detachably connected to the forward end face of said cylindrical body portion, and an opposite end closure member detachably connected to the rearward end face of said body portion, an impeller shaft extending through said rearward closure member, and having an inner end terminating within said housing, and a serrated swash-type impeller mounted on said inner end of the impeller shaft, cooperating with toothed cutter bars in a combined pumping- and shredding operation incident to rotation of the impeller shaft, said cutter bars being assembled in the form of an open ended cutter cage formfitted into said cylindrical body portion, and longitudinally divided so that one arcuate cage section is contained in said housing cover section, and the complementary arcuate cage section is contained in said fixed housing section, with the cutter bars spaced so as to provide between them elongate discharge flow passages communicating with said discharge neck, the ends of said cutter bars being fixedly connected to the cylindrical outer faces of respective semiperipheral rim members by means of screw bolts threaded into said rim members, the method of varying the spacing of said cutter bars, and thereby varying the width of said flow passages, which comprises providing additional threaded holes between those occupied by said bolts, to constitute a row of evenly and closely spaced threaded holes, providing offset cutter bars with their bolt holes offset a distance from the center line, said distance being equal to one fourth of the distance between any two mutually adjoining threaded holes of said row, said cutter bars being reversible end for end, for placing the offset either to the right or to the left, and combining a required number of offset cutter bars into cage assemblies in accordance with selected combinations of said threaded holes, so as to establish any one of the thus available bar spacing options in said complementary section of the cutter cage.
 2. The method according to claim 1, which comprises additionally providing non-offset cutter bars having their bolt holes located on the center line, and combining offset cutter bars together with one Or more of the non-offset cutter bars in accordance with selected combinations of said threaded holes, so as to provide corresponding additionally available bar spacing options.
 2. Cutter bars L, R, L, R, L, R connected to threaded holes 1, 5, 8, 12, 15 and 19 respectively.
 3. Cutter bars L, L, L, L, L connected to threaded holes 2, 6, 10, 14 and 18 respectively.
 3. The method according to claim 1, wherein said row comprises a basic series of threaded holes basically spaced so as to accommodate said cutter bars in narrowly spaced relationship, and wherein said additional holes are interposed between any two of said basically spaced holes, whereby a corresponding series of options of graduated bar spacing increments is attainable beyond said narrowly spaced relationship of the cutter bars.
 4. In the operation of a rotary pump with a housing having a cylindrical body portion longitudinally divided into a fixed section provided with a discharge neck, and a removable arcuate cover section, a forward end closure member having an inlet neck, detachably connected to the forward end face of said cylindrical body portion, and an opposite end closure member detachably connected to the rearward end face of said body portion, an impeller shaft extending through said rearward closure member, and having an inner end terminating within said housing, and a serrated swash-type impeller mounted on said inner end of the impeller shaft, cooperating with toothed cutter bars in a combined pumping- and shredding operation incident to rotation of the impeller shaft, said cutter bars being assembled in the form of an open ended cutter cage formfitted into said cylindrical body portion, and longitudinally divided so that one arcuate cage section is contained in said housing cover section, and the complementary arcuate cage section is contained in said fixed housing section, with the cutter bars spaced so as to provide between them elongate discharge flow passages communicating with said discharge neck, the ends of said cutter bars being fixedly connected to the cylindrical outer faces of respective semi-peripheral rim members by means of screw bolts threaded into said rim members, the method of varying the spacing of said cutter bars, and thereby varying the width of said flow passages, which comprises, providing additional threaded holes between those occupied by said bolts, to constitute a row of evenly and closely spaced threaded holes, comprising one centrally arranged hole and an equal number of holes symmetrically disposed on either side of the central hole, providing offset cutter bars with their bolt holes offset a distance from the center line, said distance being equal to one-fourth of the distance between any two mutually adjoining threaded holes of said row, said cutter bars being reversible end for end, for placing the offset either to the right or to the left, and combining a required number of offset cutter bars into cage assemblies in accordance with selected combinations of said threaded holes, so as to establish any one of the thus available bar spacing options in said complementary section of the cutter cage.
 4. Cutter bars L, R, C, L, R connected to threaded holes 1, 6, 10, 14 and 19 respectively.
 5. The method according to claim 4, which comprises additionally providing non-offset cutter bars having their bolt holes located on the center line, and combining offset cutter bars together with one or more of the non-offset cutter bars in accordance with selected combinations of said threaded holes, so as to provide corresponding additionally available bar spacing options.
 5. Cutter bars L, R, L, R, L connected to threaded holes 1, 6, 10, 15 and 19 respectively.
 6. Cutter bars L, L, L, L connected to threaded holes 1, 7, 13 and 19 respectively.
 6. The method according to claim 4, which comprises providing said row having a basic series of threaded holes basically spaced for accommodating a series of cutter bars in narrowly spaced relationship and occupying said rim members substantially from end to end, and wherein said additional holes are interposed between any two of said basically spaced holes, whereby a corresponding series of options of graduated bar spacing increments is attainable beyond said narrowly spaced relationship of the cutter bars.
 7. The method according to claim 4, which comprises providing said row to have a basic series of threaded holes basically spaced so as to accommodAte said cutter bars in narrowly spaced relationship, and wherein a pair of additional threaded holes are interposed and accommodated between any two of said basically spaced holes, and occupying said rim members substantially from end to end, whereby a corresponding series of options of graduated bar spacing increments is attainable beyond said narrowly spaced relationship of the cutter bars.
 8. The method according to claim 4, which comprises providing said row to have holes numbered 1 through 19 including seven basic holes numbered 1, 4, 7, 10, 13, 16 and 19 basically spaced for accommodating a series of cutter bars in narrowly spaced relationship, and substantially occupying said rim members from end to end, whereby options of graduated bar spacing increments are attainable, with R designating an offset cutter bar having bolt holes offset to the right of center line, L designating an offcenter cutter bar having bolt holes offset to the left of center line, and C designating a non-offset cutter bar having bolt holes located on center, said options comprising
 9. A rotary pump with a housing having a cylindrical body portion longitudinally divided into a fixed section provided with a discharge neck, and a removable arcuate cover section, a forward end closure member having an inlet neck, detachably connected to the forward end face of said cylindrical body portion, and an opposite end closure member detachably connected to the rearward end face of said body portion, an impeller shaft extending through said rearward closure member, and having an inner end terminating within said housing, and a serrated swash-type impeller mounted on said inner end of the impeller shaft, cooperating with a toothed cutter bars in a combined pumping- and shredding operation incident to rotation of the impeller shaft. said cutter bars being assembled in the form of an open ended cutter cage formfitted into said cylindrical body portion, and longitudinally divided so that one arcuate cage section is contained in said housing cover section, and the complementary arcuate cage section is contained in said fixed housing section, with the cutter bars spaced so as to provide between them elongate discharge flow passages communicating with said discharge neck, the ends of said cutter bars being fixedly connected to the cylindrical outer faces of respective semi-peripheral rim members by means of screw bolts threaded into said rim members, characterized in that the discharge section of the cage comprises a pair of semi-peripheral end rim members each provided with a row of closely spaced radially directed threaded holes, comprising one centrally arranged hole and equal numbers of identical threaded holes, disposed symmetrically on either side of the central hole, an arrangement of off-center cutter bars connected to said rim members through offcenter bolt holes in said cutter bars, located off center a distance equal to one quarter of the distance between any two mutually adjacent threaded holes, with the offsets disposed in accordance with a predetermined flow passage spacing between said bars.
 10. A rotary pump with a housing having a cylindrical body portion longitudinally divided into a fixed section provided with a discharge neck, and a removable arcuate cover section, a forward end closure member having an inlet neck, detachably connected to the forward end face of saiD cylindrical body portion, and an opposite end closure member detachably connected to the rearward end face of said body portion, an impeller shaft extending through said rearward closure member, and having an inner end terminating within said housing, and a serrated swash-type impeller mounted on said inner end of the impeller shaft, cooperating with toothed cutter bars in a combined pumping- and shredding operation incident to rotation of the impeller shaft, said cutter bars being assembled in the form of an openended cutter cage formfitted into said cylindrical body portion, and longitudinally divided so that one arcuate cage section is contained in said housing cover section, and the complementary arcuate cage section is contained in said fixed housing section, with the cutter bars spaced so as to provide between them elongate discharge flow passages communicating with said discharge neck, the ends of said cutter bars being fixedly connected to the cylindrical outer faces of respective semi-peripheral rim members by means of screw bolts threaded into said rim members, characterized in that the discharge section of the cage comprises a pair of semi-peripheral end rim members each provided with a row of closely spaced radially directed threaded holes, comprising one centrally arranged hole and equal numbers of identical threaded holes, disposed symmetrically on either side of the central hole, and an arrangement of cutter bars, which in turn comprises off-center cutter bars connected to said rim members, said cutter bars located off center a distance equal to one quarter of the distance between any two mutually adjacent threaded holes, and at least one non-offcenter cutter bar, all of said cutter bars being combined and with said offsets disposed in accordance with a predetermined flow passage spacing between said bars.
 11. The pump according to claim 10 wherein said row comprises at least 19 threaded holes numbered 1 through 19, including seven basically spaced holes assigned to numbers 1, 4, 7, 10, 13, 16 and 19 of said row, and an assembly of cutter bars with R designating a cutter bar having bolt holes offset to the right, L designating bolt holes offset to the left, and C designating a cutter bar with bolt holes on center, said assembly comprising Cutter bars R, C, L, R, C, L connected to threaded holes 2, 5, 8, 12, 15 and 19 respectively.
 12. The pump according to claim 10 wherein said row comprises at least 19 threaded holes numbered 1 through 19, including seven basically spaced holes assigned to numbers 1, 4, 7, 10, 13, 16, and 19 of said row, and an assembly of cutter bars with R designating a cutter bar having bolt holes offset to the right, L designating bolt holes offset to the left, and C designating a cutter bar with bolt holes on center, said assembly comprising cutter bars L, R, L, R, L, R connected to threaded holes 1, 4, 8, 12, 15 and 19 respectively.
 13. The pump according to claim 10 wherein said row comprises at least 19 threaded holes numbered 1 through 19, including seven basically spaced holes assigned to numbers 1, 4, 7, 10, 13, 16, and 19 of said row, and an assembly of cutter bars with R designating a cutter bar having bolt holes offset to the right, L designating bolt holes offset to the left, and C designating a cutter bar with bolt holes on center, said assembly comprising cutter bars L, L, L, L, L connected to threaded holes 2, 6, 10, 14 and 18 respectively.
 14. The pump according to claim 10, wherein said row comprises at least 19 threaded holes numbered 1 through 19, including seven basically spaced holes assigned to numbers 1, 4, 7, 10, 13, 16 and 19 of said row, and an assembly of cutter bars with R designating a cutter bar having bolt holes offset to the right, L designating bolt holes offset to the left, and C designating a cutter bar with bolt holes on center, said assembly comprising cutter bars L, R, C, L, R connected to threaded holes 1, 6, 10, 14 and 19 resPectively.
 15. The pump according to claim 10, wherein said row comprises at least 19 threaded holes number 1 through 19, including seven basically spaced holes assigned to number 1, 4, 7, 10, 13, 16 and 19 of said row, and an assembly of cutter bars with R designating a cutter bar having bolt holes offset to the right, L designating bolt holes offset to the left, and C designating a cutter bar with bolt holes on center, said assembly comprising cutter bars L, R, L, R, L connected to threaded holes 1, 6, 10, 15 and 19 respectively.
 16. The pump according to claim 10, wherein said row comprises at least 19 threaded holes numbered 1 through 19, including seven basically spaced holes assigned to numbers 1, 4, 7, 10, 13, 16 and 19 of the said row, and an assembly of cutter bars with R designating a cutter bar having bolt holes offset to the right, L designating bolt holes offset to the left, and C designating a cutter bar with bolt holes on center, said assembly comprising cutter bars L, L, L, L connected to threaded holes 1, 7, 13 and 19 respectively. 